[R] Using str() in a function.

Bert Gunter gunter.berton at gene.com
Fri Jul 15 19:44:55 CEST 2011

-- Bert

On Fri, Jul 15, 2011 at 10:31 AM, andrewH <ahoerner at rprogress.org> wrote:
> Thanks, everybody, this has been very edifying. One last question:
> It seems that sometimes when a function returns something and you don't
> assign it, it prints to the console, and sometimes it doesn't. I'm not sure
> I understand which is which. My best current theory is that, if the function
> returns NULL, by itself and not as part of some larger object, it does not
> print it, but non-null values are printed. Is that correct?

-- No.
It depends on whether the function uses invisible() in the return,

If invisible() is not used and the value is not assigned, it's
printed. Otherwise not.cf:

f <- function()NULL
g <- function()invisible(NULL)

f() ## NULL is printed
g() ## nothing printed

z1 <- f() ## nothing printed
z2 <- g() ## nothing printed

z1 ## NULL
z2 ##NULL


> Thanks! Andrew
> --
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"Men by nature long to get on to the ultimate truths, and will often
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-- Maimonides (1135-1204)

Bert Gunter
Genentech Nonclinical Biostatistics

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